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Large-scale manufacturing of aluminum alloy plate extruded from subsize billet by new porthole-equal channel angular processing technique 被引量:4
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作者 石磊 杨合 +2 位作者 郭良刚 党利 张君 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2014年第5期1521-1530,共10页
To manufacture plate by the combination of equal channel angular processing (ECAP) and porthole die extrusion techniques, a novel technique, namely portholes-equal channel angular processing (P-ECAP), was studied.... To manufacture plate by the combination of equal channel angular processing (ECAP) and porthole die extrusion techniques, a novel technique, namely portholes-equal channel angular processing (P-ECAP), was studied. Extrusion of AL6005A plate used for the bullet train plate was investigated by finite element method. The relevant porthole dies involving ECAP technique in channels were designed. Dimensional changes in the scrap part of the extrudate obtained after extrusion from the P-ECAP die, with different channel angles, were predicted. Effects of the channel angle and extrusion speed on the maximum temperature of the workpiece and other field variables were evaluated. At the channel angle of 160° of P-ECAP dies, the extrudate exhibited the optimal performance and the least amount of extrudate scrap was obtained. The optimal extrusion speed was 3-5 mm/s. Moreover, with the increase in ram speed from 1 to 9 mm/s, the peak extrusion load increased by about 49% and the maximum temperature was increased by about 70 ℃. The effective strain exhibited ascending trend in the comer of the ECAP deformation zone. In the solder seam and the side of die bearing of extrudate, the maximum principal stresses were tensile stress. 展开更多
关键词 subsize billet porthole die equal channel angular processing (ECAP) EXTRUSION
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A new method of characterizing equivalent strain for equal channel angular processing 被引量:1
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作者 赵军 王振华 +3 位作者 孙淑华 赵德利 任利国 傅万堂 《Journal of Central South University》 SCIE EI CAS 2009年第3期349-353,共5页
In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material within the range of certain passes for equal channel angular processing (ECAP), a new ... In order to establish the quantitative relationship between equivalent strain and the performance index of the deformed material within the range of certain passes for equal channel angular processing (ECAP), a new approach to characterize the equivalent strain was proposed. The results show that there exists better accordance between mechanical property (such as hardness or strength) and equivalent strain after rolling and ECAP in a certain range of deformation amount, and Gauss equation can be satisfied among the equivalent strain and the mechanical properties for ECAP. Through regression analysis on the data of hardness and strength after the deformation, a more generalized expression of equivalent strain for ECAP is proposed as:ε=k0exp[-(k1M-k2)^2], where M is the strength or hardness of the material, k1 is the modified coefficient (k1∈ (0, 1)), ko and k2 are two parameters dependent on the critical strain and mechanical property that reaches saturation state for the material, respectively. In this expression the equivalent strain for ECAP is characterized novelly through the mechanical parameter relating to material property rather than the classical geometry equation. 展开更多
关键词 equal channel angular processing (ECAP) equivalent strain mechanical property characterizing method
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Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angular extrusion in semi-solid isothermal treatment 被引量:9
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作者 姜巨福 罗守靖 《Transactions of Nonferrous Metals Society of China》 SCIE EI CAS CSCD 2006年第6期1313-1319,共7页
Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angularextrusion(ECAE) in semi-solid isothermal treatment was investigated. The results show that withincreasing semi-solid isothermal treatment te... Microstructure evolution of processed Mg-Al-Zn alloy by equal channel angularextrusion(ECAE) in semi-solid isothermal treatment was investigated. The results show that withincreasing semi-solid isothermal treatment temperature, the a phase solid grain size of processedMg-Al-Zn alloy by ECAE increases firstly due to coarsening of a phase solid grains, then decreasesdue to melting of a phase solid grains. With the increase of extrusion passes during ECAE, the aphase solid grain size in the following semi-solid isothermal treatment decreases. The a phase solidgrain size of processed Mg-Al-Zn alloy by ECAE under route B_C is the smallest, while the a phasesolid grain size of processed material by ECAE under route A is the largest. The primary mechanismof spheroid formation depends on the melting of recrystallizing boundaries and diffusion of soluteatoms in the semi-solid state. 展开更多
关键词 magnesium alloy Mg-Al-Zn alloy equal channel angular extrusion isothermaltreatment semi-solid processing
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Shape characterization of sand particles based on digital image processing technology 被引量:3
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作者 Zhou Xinwen Liu Jianzhong +2 位作者 Zhu Jiang Mao Yonglin Liu Jiaping 《Journal of Southeast University(English Edition)》 EI CAS 2020年第3期313-321,共9页
To characterize the shape of sand particles for concrete,a new method is proposed based on digital image processing(known as the DIP method).By analyzing sand particles projection,the length,width and thickness of san... To characterize the shape of sand particles for concrete,a new method is proposed based on digital image processing(known as the DIP method).By analyzing sand particles projection,the length,width and thickness of sand were measured to characterize particle form.The area and perimeter were measured to characterize particle angularity.The results of the DIP method and Vernier caliper were compared to examine the accuracy of the DIP method.The sample size test was conducted to show the statistical significance of shape results measured by the DIP method.The practicality of the DIP method was verified by instance analysis.The results show that aspect ratios and roundness measured by the DIP method are equal to ones by the Vernier caliper.Results by DIP are dependent on the sand particle number,and at least 350 particles should be measured to represent the overall shape property of sand.The results show that the DIP method is able to distinguish the differences in the shape of sand particles.It achieves the direct measurement of sand particle thickness,and the characterization results of sand aspect ratios and roundness are accurate,statistically significant and practical.Therefore,the DIP method is suitable for sand particle shape characterization. 展开更多
关键词 particle shape SAND FORM angularITY digital image processing
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Microstructural Development of Fe-20mass%Cr Alloys and Pure Copper Processed by Equal-Channel Angular Pressing
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作者 Muhammad Rifai Ryosuke Haga +1 位作者 Hiroyuki Miyamoto Hiroshi Fujiwara 《Materials Sciences and Applications》 2013年第4期250-257,共8页
Microstructural development of ultra low C, N, Fe-Cr alloy and pure copper processed by equal-channel angular pressing (ECAP) have been examined focusing on the initial stage of the formation of ultrafine grain struct... Microstructural development of ultra low C, N, Fe-Cr alloy and pure copper processed by equal-channel angular pressing (ECAP) have been examined focusing on the initial stage of the formation of ultrafine grain structure. Fe-Cr alloys were pressed at 423 K while pure copper at room temperature for 1 to 3 passes via the route Bc to compare at the equivalent homologous temperature. Microstructural evolutions were characterized by electron backscatter diffraction (EBSD) image and transmission electron microscopy (TEM). It was found that deformation structures were mostly deformation-induced subboundaries in both the materials after one pass, but the fraction of high-angle grain boundary became higher in the Fe-Cr alloys than in pure copper in subsequent passes by increasing misorientation of the boundaries. The more enhanced formation of high angle boundaries in Fe-Cr alloys was discussed in terms of the nature of crystal slip of FCC and BCC structures. 展开更多
关键词 EBSD Copper Ferritic STAINLESS Steel Equal-Channel angular processing (ECAP) GRAIN Boundaries
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沥青路面粗集料棱角性衰变规律及与抗滑性能的关联
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作者 季节 崔颖怡 +3 位作者 任万艳 文龙 蒋天昊 王佳妮 《北京工业大学学报》 北大核心 2026年第2期209-219,共11页
为分析沥青路面粗集料棱角性的衰变规律及其与抗滑性能的关联,分别通过二维数字图像处理和三维激光扫描技术对现场芯样回收的表面层粗集料和室内洛杉矶磨耗的粗集料进行检测,获取其二维图像和三维数字模型后对集料棱角性进行量化分析,... 为分析沥青路面粗集料棱角性的衰变规律及其与抗滑性能的关联,分别通过二维数字图像处理和三维激光扫描技术对现场芯样回收的表面层粗集料和室内洛杉矶磨耗的粗集料进行检测,获取其二维图像和三维数字模型后对集料棱角性进行量化分析,使用动态摩擦因数仪对路面抗滑性能进行测试。采用二维棱角性评价指标凸度(convexity,CV)、轴度(aspect ratio,AS)、圆度(roundness,RO)和三维棱角性评价指标针度(needleness,ND)、片度(flatness,CS)、球度(sphericity,DS)、形状因子(shape factor,SF)评价棱角性,分析其变化规律并优选棱角性评价指标,然后结合微观纹理指标构建路面抗滑性能预测模型。研究表明,由于集料的放置形式对二维成像影响显著,故二维棱角性评价指标不适用于评价其衰变规律,而三维棱角性评价方法能较好表征集料形态变化特征,且选用三维棱角性评价指标DS和SF构建的路面抗滑性能预测模型精度高达80%。 展开更多
关键词 道路工程 粗集料棱角性 三维激光扫描 数字图像处理 抗滑性能 机器学习
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Microstructure and Properties of Mg-12Gd-3Y-0.5Zr Alloys Processed by ECAP and Extrusion 被引量:2
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作者 朱荣 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 2011年第6期1128-1132,共5页
Equal channel angular pressing (ECAP) processing and conventional extrusion (Ex) were applied to the Mg-12Gd-3Y-0.5Zr (wt%) magnesium alloy in order to evaluate the potential improvement in the mechanical proper... Equal channel angular pressing (ECAP) processing and conventional extrusion (Ex) were applied to the Mg-12Gd-3Y-0.5Zr (wt%) magnesium alloy in order to evaluate the potential improvement in the mechanical properties. The ECAP experiment was conducted at 380 ℃ in a die having an included angle of 90° between two channels by the Bc route with the billet rotated by 90° about its longitudinal axis. Subsequently, some billets were processed by conventional extrusion at 300 ℃. The microstructures were examined by X-ray diffraction (XRD), optical microscopy and transmission electron microscopy (TEM). The experimental results indicate that the grain size is refined effectively, but the basal planes are highly inclined (about 40o) from the extrusion axis introduced by ECAP, which impairs the grain boundary strengthening effect. The conventional extrusion, following the ECAP, can modify the grains in hard orientation. Based on grain boundary strengthening due to ECAP and texture strengthening due to Ex, the strength is improved effectively. The enhanced activity of the non-basal slips, due to the refined grains and the reduction in c/a ratio, is responsible for good ductility and high strain hardening rate in samples obtained by the two-step process. 展开更多
关键词 magnesium alloy equal channel angular pressing thermomechanical processing TEXTURE
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Mechanical responses, texture and microstructural evolution of high purity aluminum deformed by equal channel angular pressing 被引量:4
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作者 汪冰峰 孙杰英 +2 位作者 邹金佃 VINCENT Sherman 李娟 《Journal of Central South University》 SCIE EI CAS CSCD 2015年第10期3698-3704,共7页
Ultrafine-grained(UFG) high purity aluminum exhibits a variety of attractive mechanical properties and special deformation behavior. Equal channel angular pressing(ECAP) process can be used to easily and effectively r... Ultrafine-grained(UFG) high purity aluminum exhibits a variety of attractive mechanical properties and special deformation behavior. Equal channel angular pressing(ECAP) process can be used to easily and effectively refine metals. The microstructure and microtexture evolutions and grain boundary characteristics of the high purity aluminum(99.998%) processed by ECAP at room temperature are investigated by means of TEM and EBSD. The results indicate that the shear deformation resistance increases with repeated EACP passes, and equiaxed grains with an average size of 0.9 μm in diameter are formed after five passes. Although the orientations distribution of grains tends to evolve toward random orientations, and microtextures(80°, 35°, 0°),(40°, 75°, 45°) and(0°, 85°, 45°) peak in the sample after five passes. The grain boundaries in UFG aluminum are high-angle geometrically necessary boundaries. It is suggested that the continuous dynamic recrystallization is responsible for the formation of ultrafine grains in high purity aluminum. Microstructure evolution in the high purity aluminum during ECAP is proposed. 展开更多
关键词 equal channel angular processing(ECAP) aluminum grain refinement microstructure mechanical property
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Controlling Corrosion Resistance of a Biodegradable Mg–Y–Zn Alloy with LPSO Phases via Multi-pass ECAP Process 被引量:5
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作者 Li-Sha Wang Jing-Hua Jiang +3 位作者 Bassiouny Saleh Qiu-Yuan XieQiong Xu Huan Liu Ai-Bin Ma 《Acta Metallurgica Sinica(English Letters)》 SCIE EI CAS CSCD 2020年第9期1180-1190,共11页
Mg-RE(rear earth) alloys with long period stacking(LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y1 Zn0.5 alloys wi... Mg-RE(rear earth) alloys with long period stacking(LPSO) structures have great potential in biomedical applications. The present work focused on the microstructure and corrosion behaviors of Mg 98.5 Y1 Zn0.5 alloys with 18 R LPSO structure after equal channel angular pressing(ECAP). The results showed that the ECAP process changed the grain size and the distribution of LPSO particles thus controlled the total corrosion rates of Mg 98.5 Y1 Zn0.5 alloys. During the ECAP process from 0 p to 12 p, the grain size reduced from 160–180 μm(as-cast) to 6–8 μm(12 p). The LPSO structures became kinked(4 p), then started to be broken into smaller pieces(8 p), and at last comminuted to fine particles and redistributed uniformly inside the matrix(12 p). The improvement in the corrosion resistance for ECAP samples was obtained from 0 p to 8 p, with the corrosion rate reduced from 3.24 mm/year(0 p) to 2.35 mm/year(8 p) in simulated body fluid, and the 12 p ECAP alloy exhibited the highest corrosion rate of 4.54 mm/year. 展开更多
关键词 Corrosion behavior Long period stacking ordered phase Magnesium alloys Equal channel angular pressing(ECAP)process Biomaterials
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A super-high angular resolution principle for coded-mask X-ray imaging beyond the diffraction limit of a single pinhole
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作者 Chen Zhang Shuang-Nan Zhang 《Chinese Journal of Astronomy and Astrophysics》 CSCD 2009年第3期333-340,共8页
High angular resolution X-ray imaging is always useful in astrophysics and solar physics. In principle, it can be performed by using coded-mask imaging with a very long mask-detector distance. Previously, the diffract... High angular resolution X-ray imaging is always useful in astrophysics and solar physics. In principle, it can be performed by using coded-mask imaging with a very long mask-detector distance. Previously, the diffraction-interference effect was thought to degrade coded-mask imaging performance dramatically at the low energy end with its very long mask-detector distance. The diffraction-interference effect is described with numerical calculations, and the diffraction-interference cross correlation reconstruction method (DICC) is developed in order to overcome the imaging performance degradation. Based on the DICC, a super-high angular resolution principle (SHARP) for coded-mask X-ray imaging is proposed. The feasibility of coded mask imaging beyond the diffraction limit of a single pinhole is demonstrated with simulations. With the specification that the mask element size is 50 × 50 μm^2 and the mask-detector distance is 50 m, the achieved angular resolution is 0.32arcsec above about 10keV and 0.36arcsec at 1.24keV (λ = 1 nm), where diffraction cannot be neglected. The on-axis source location accuracy is better than 0.02 arcsec. Potential applications for solar observations and wide-field X-ray monitors are also briefly discussed. 展开更多
关键词 INSTRUMENTATION high angular resolution - techniques image processing - telescopes
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Modified scaling angular spectrum method for numerical simulation in long-distance propagation
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作者 Xiao-Yi Chen Ya-Xuan Duan +2 位作者 Bin-Bin Xiang Ming Li Zheng-Shang Da 《Chinese Physics B》 SCIE EI CAS CSCD 2021年第3期266-274,共9页
The angular method(AS)cannot be used in long-distance propagation because it produces severe numerical errors due to the sampling problem in the transfer function.Two ways can solve this problem in AS for long-distanc... The angular method(AS)cannot be used in long-distance propagation because it produces severe numerical errors due to the sampling problem in the transfer function.Two ways can solve this problem in AS for long-distance propagation.One is zero-padding to make sure that the calculation window is wide enough,but it leads to a huge calculation burden.The other is a method called band-limited angular spectrum(BLAS),in which the transfer function is truncated and results in that the calculation accuracy decreases as the propagation distance increases.In this paper,a new method called modified scaling angular spectrum(MSAS)to solve the problem for long-distance propagation is proposed.A scaling factor is introduced in MSAS so that the sampling interval of the input plane can be adjusted arbitrarily unlike AS whose sampling interval is restricted by the detector’s pixel size.The sampling interval of the input plane is larger than the detector’s pixel size so the size of calculation window suitable for long-distance field propagation in the input plane is smaller than the size of the calculation window required by the zero-padding.Therefore,the method reduces the calculation redundancy and improves the calculation speed.The results from simulations and experiments show that MSAS has a good signal-to-noise ratio(SNR),and the calculation accuracy of MSAS is better than BLAS. 展开更多
关键词 angular spectrum DIFFRACTION Fourier optics and signal process
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Analysis of the Manufactured Tolerances with the Three-Dimensional Method of Angular Chains of Dimensions Applied to a Cylinder Head of Car Engine
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作者 Aida Mezghani Alain Bellacicco +2 位作者 Jamel Louati Alain Rivière Mohamed Haddar 《Engineering(科研)》 2010年第10期771-779,共9页
This paper proposes an analysis method of the manufactured tolerances applied to a cylinder head of car engine. This method allows to determine the manufacturing tolerances in the case of angular chains of dimensions ... This paper proposes an analysis method of the manufactured tolerances applied to a cylinder head of car engine. This method allows to determine the manufacturing tolerances in the case of angular chains of dimensions and to check its correspondence with the functional tolerances. The objective of this work is to analyze two parameterized functions: the angular defect Δα and the projected length lg of the toleranced surface. The angular defects are determined from the precision of the machine tools, we consider only the geometrical defects (position and orientation of surfaces), making the assumption that the form defects are negligible. The manufactured defect is determined from these two parameterized functions. Then it will be compared with the functional condition in order to check if the selected machining range allows, at end of the manufacturing process, to give a suitable part. 展开更多
关键词 Three-Dimensional TOLERANCING Manufacturing process Toleranced Surface angular DEFECT
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粗集料棱角性及其对沥青混合料性能影响研究
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作者 于浩 杨杰 +2 位作者 何兆益 秦旻 杨志强 《重庆交通大学学报(自然科学版)》 北大核心 2025年第6期26-34,44,共10页
为评价粗集料的棱角性并研究其对混合料性能的影响规律,利用Image-pro plus数字图像处理软件分析了集料样本数量和摆放面的合理性,对不同料源和不同加工工艺的粗集料进行了棱角性评价,并在此基础上开展了沥青混合料路用性能试验。结果表... 为评价粗集料的棱角性并研究其对混合料性能的影响规律,利用Image-pro plus数字图像处理软件分析了集料样本数量和摆放面的合理性,对不同料源和不同加工工艺的粗集料进行了棱角性评价,并在此基础上开展了沥青混合料路用性能试验。结果表明:粗集料的棱角性与石料的加工特性和料源特性密切相关。高强度石料能更好地抵抗破碎和磨损,保持良好的棱角性;多级破碎工艺可增加集料颗粒的破碎面,形成更多棱角,从而提高粗集料的棱角性;粗集料的棱角性对AC-20沥青混合料性能有显著影响。随着平均棱角参数由1.076 4增加到1.082 5、1.083 2、 1.129 1,混合料的动稳定度分别提高了12.9%、15.8%、 55.6%,弯拉应变则分别增加了6.3%、8.5%、 17.5%;提高粗集料棱角性有利于提升混合料高温和低温性能,但相同压实功下,棱角性强的集料更难压密,导致空隙增大,降低混合料的水稳定性,因此对于粗集料棱角性较高的沥青混合料,施工中应优化压实工艺,以获得良好的压实。 展开更多
关键词 道路工程 路用性能 数字图像处理技术 粗集料 棱角性
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基于串、并混联六自由度调整机构的姿态测量
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作者 杜润泽 乔晓旭 +1 位作者 罗怡 王晓东 《机械设计与制造工程》 2025年第7期65-69,共5页
针对跟踪准直仪中光学元件姿态精密调整的需要,设计了一种串、并混联六自由度调整机构。引入激光模拟待调整零件,经图像处理后得到机构姿态变化引起光斑中心位置变化的规律,获得了滑台位移-姿态调整关系,对模型得到的理论值进行修正。... 针对跟踪准直仪中光学元件姿态精密调整的需要,设计了一种串、并混联六自由度调整机构。引入激光模拟待调整零件,经图像处理后得到机构姿态变化引起光斑中心位置变化的规律,获得了滑台位移-姿态调整关系,对模型得到的理论值进行修正。实验表明,滑台移动5μm,绕X、Y轴转动时的角度分别为2.0″±0.1″和1.4″±0.1″,实现了对光学元件姿态的精密调整。 展开更多
关键词 串、并混联调整机构 姿态调整 图像处理 激光成像 角度分辨率
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工艺参数对等径角挤压钢/铝复合微观组织的影响
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作者 刘阳 徐俊瑞 +1 位作者 范昱琪 陈炳男 《塑性工程学报》 北大核心 2025年第10期111-124,共14页
基于等径角挤压工艺,对6061铝合金和20低碳钢进行复合实验,探究工艺参数挤压速度和挤压温度对钢/铝复合微观组织的影响。结果表明,随着挤压速度的增加,钢侧晶粒细化。在挤压速度为100 mm·min^(-1)时晶粒尺寸减小至Φ13.55μm,较10 ... 基于等径角挤压工艺,对6061铝合金和20低碳钢进行复合实验,探究工艺参数挤压速度和挤压温度对钢/铝复合微观组织的影响。结果表明,随着挤压速度的增加,钢侧晶粒细化。在挤压速度为100 mm·min^(-1)时晶粒尺寸减小至Φ13.55μm,较10 mm·min^(-1)时降低了18%。同时,界面缝隙随挤压速度的提高而减小,低速时缝隙明显, 100 mm·min^(-1)时缝隙宽度降至0.37μm。挤压温度升高对钢和铝两侧组织产生显著影响。钢侧晶粒在挤压温度为425℃下显著细化,形成由拉长粗晶和细小等轴晶组成的组织,且小角度晶界占比明显增加;在挤压温度为225℃下回复组织增多并伴随一定数量的再结晶组织。铝侧则随温度升高晶粒长大,小角度晶界占比亦显著增加;再结晶在变形基体中形核,位错密度下降。经520℃保温1 h热处理后,挤压温度较高的试样界面金属间化合物层厚度显著增加,界面层内生成的新相主要为Fe_(2)Al_(5)和FeAl_(3)。 展开更多
关键词 钢/铝复合 等径角挤压 微观组织 工艺参数
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工艺参数对等通道转角拉伸7075铝合金截面椭圆度的影响
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作者 邓善萍 何涛 +3 位作者 陈细林 杜向阳 李健 朱家赟 《塑性工程学报》 北大核心 2025年第4期97-105,共9页
针对7075铝合金在等通道转角拉伸(ECAD)工艺后试样截面出现近似椭圆的现象,通过有限元模拟揭示了试样经ECAD后截面椭圆的形成机制,利用实验与有限元分析相结合探究了模具内角、模具外角、拉伸速度、拉伸道次以及拉伸路径对ECAD 7075铝... 针对7075铝合金在等通道转角拉伸(ECAD)工艺后试样截面出现近似椭圆的现象,通过有限元模拟揭示了试样经ECAD后截面椭圆的形成机制,利用实验与有限元分析相结合探究了模具内角、模具外角、拉伸速度、拉伸道次以及拉伸路径对ECAD 7075铝合金截面椭圆度的影响规律及其内在机理。结果表明:随着模具内角和模具外角的增大,截面椭圆度减小,且模具内角的影响程度大于模具外角;拉伸速度对截面椭圆度的影响不明显;截面椭圆度随着拉伸道次的增加而增大,但增幅逐渐减小;不同拉伸路径对椭圆度的影响程度不同,其大小顺序为C路径>A路径>B路径。 展开更多
关键词 7075铝合金 等通道转角拉伸 椭圆度 工艺参数 有限元
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Array processing for the GD signal model with angular spread
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作者 ZHU Shimeng, SONG Mingkai GONG Xianyi (Hangzhou Applied Acoustics Research Institute, Zhejiang 311400 China) 《Chinese Journal of Acoustics》 1992年第4期307-316,共10页
Array processing is to process the signals carried by the propagating waves received at an array of sensors. When the signals propagate through the practical random time-variant medium, their wavefronts can show the p... Array processing is to process the signals carried by the propagating waves received at an array of sensors. When the signals propagate through the practical random time-variant medium, their wavefronts can show the progressive losses of coherence with increasing spatial separation. These decorrelations of wavefronts result in an angular spread in the wavenumber spectrum centered about the true signal dircction-of-arrival. This paper puts the emphasis upon the array processing of the angular-spread signal which is called the Generalized Directional (GD) signal and aims to match array processing to this signal model in the energy sense. In this paper, we also present a method of the computer simulation of the generalized directional signal model. Some results of computer simulation experiments and lake-tests in Xinanjiang River are given. 展开更多
关键词 Array processing for the GD signal model with angular spread MVDR
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粗集料棱角性的图像评价方法 被引量:35
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作者 汪海年 郝培文 +1 位作者 肖庆一 刘丽 《东南大学学报(自然科学版)》 EI CAS CSCD 北大核心 2008年第4期637-641,共5页
利用自行研制的粗集料形态特征研究系统,分别采用颗粒周长法与分形几何法,提出粗糙度与分形维数2个指标对粗集料的棱角特征进行评价.将其计算结果与目前侵蚀膨胀法的表面参数指标进行了对比分析,并采用粗集料松装空隙率对粗糙度与分形维... 利用自行研制的粗集料形态特征研究系统,分别采用颗粒周长法与分形几何法,提出粗糙度与分形维数2个指标对粗集料的棱角特征进行评价.将其计算结果与目前侵蚀膨胀法的表面参数指标进行了对比分析,并采用粗集料松装空隙率对粗糙度与分形维数2个图像指标进行了验证.研究表明:粗集料的粗糙度、分形维数与表面参数具有良好的一致性,均可以较好地表征粗集料的棱角性.粗集料的棱角特性与集料的粒径尺寸具有一定的相关性,集料粒径越大,其棱角性越弱.对于所采用的材料,卵石的棱角性最差,石灰岩、花岗岩、玄武岩与安山岩4个集料的棱角性差异并不显著. 展开更多
关键词 道路工程 粗集料 棱角性 数字图像处理
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等径弯曲通道变形(ECAP)的研究现状及发展趋势 被引量:21
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作者 张玉敏 丁桦 +1 位作者 孝云祯 杨春征 《材料与冶金学报》 CAS 2002年第4期258-262,共5页
等径弯曲通道变形 (equalchannelangularprocessing,ECAP)是使材料经受强烈塑性变形的一种加工方法 .本文介绍ECAP的国内外发展概况 ,对其方法和影响因素等做了概述 。
关键词 研究现状 发展趋势 等径弯曲通道变形 强烈塑性变形 加工方法 ECAP
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不同路径等通道转角挤压镁合金的结构与力学性能 被引量:26
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作者 刘英 陈维平 +2 位作者 张大童 张卫文 李元元 《华南理工大学学报(自然科学版)》 EI CAS CSCD 北大核心 2004年第10期10-14,共5页
为了研究等通道转角挤压时不同工艺路径对镁合金微观结构及性能的影响 ,采用模角φ =12 0°的模具 ,以A ,BA,BC,C四种工艺路径对AZ31镁合金进行了等通道转角挤压 ,分析测试了室温下挤压试样的微观结构及性能 .结果表明 ,相比于A ,B... 为了研究等通道转角挤压时不同工艺路径对镁合金微观结构及性能的影响 ,采用模角φ =12 0°的模具 ,以A ,BA,BC,C四种工艺路径对AZ31镁合金进行了等通道转角挤压 ,分析测试了室温下挤压试样的微观结构及性能 .结果表明 ,相比于A ,BA,C路径挤压 ,BC 路径挤压容易实现较多的挤压道次和变形量 ;多道次挤压后 ,镁合金的晶粒得到显著细化 ,力学性能也显著改善 ,但不同路径的影响不同 .当挤压 12道次时 ,BC,BA 路径挤压试样的屈服强度显著下降 ,延伸率大幅度提高 ;A ,C路径挤压试样的屈服强度变化较小 ,延伸率的提高幅度也小 . 展开更多
关键词 等通道转角挤压 工艺路径 镁合金 微观结构 力学性能
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